Fix documentation of the `print` command
Fix documentation of the `print` command

The documentation of the `print` command still refers to the plugin
name as "helloworld".  Change it to "cookbook-plugin".

Change-Id: I67db42368719825669cc5a37026930d388147313

GerritCodeReview/plugins_cookbook-plugin,GerritCodeReview/plugins_cookbook-plugin,akilman/appd-hackathon-2016,pgroudas/gerrit-keep-approvals,akilman/appd-hackathon-2016,GerritCodeReview/plugins_cookbook-plugin,akilman/appd-hackathon-2016,pgroudas/gerrit-keep-approvals